Current Insights On The Use Of Orthotics For Limb Length Discrepancy And Morton’s Syndrome

Author(s): 
Guest Clinical Editor: Joseph C. D’Amico, DPM, DABPO

These expert panelists share their approach to limb length discrepancies and the roles that orthotics and orthotic modifications can play in addressing these discrepancies. They also offer pearls on conservative care for Morton’s syndrome.

Q:

What method do you use for assessing limb length discrepancy and how do you determine if the degree of discrepancy is contributing to the presenting pathology?

A:

As Joseph D’Amico, DPM, notes, most experts and texts indicate that a limb length discrepancy of 1 to 1.5 cm is extremely common and does not produce pathological effects in the average individual. However, he says almost everyone agrees that discrepancies greater than 1.5 cm and certainly those over 2.0 cm produce pathomechanical consequences and symptomatology.

   “Determining the importance, degree of abnormality and correction for leg length discrepancies remains one of the most controversial issues in medicine today,” notes Lou Pack, DPM.

   Acknowledging how comprehensive the subject of limb length discrepancy is, Dr. Pack says physicians often focus on the best method of measuring length differences but emphasizes it is more important to focus first on whether those differences are structural or functional.

   “If we don’t, those measurements, as accurate as they may be, may at times be worthless,” says Dr. Pack.

   J. David Skliar, DPM, cautions that limb length discrepancy measurement is only meaningful when the patient is standing with equal weight on both limbs (if possible) in an anatomical stance position. Both he and Dr. D’Amico suggest palpating the anterior superior iliac spine or posterior superior iliac spine, and then have the patient place his or her thumbs in the same position, which can help achieve a more accurate visual impression of which side is elevated.

   One should place index cards under the short limb’s heel in increasing numbers until the pelvis appears level. At this point, Dr. Skliar says one should remove the index cards and measure the thickness of the cards with a standard ruler.

   Similarly, Dr. Skliar advises that the simplest way of determining if the limb length discrepancy is related to presenting pathology is to place a temporary lift of at least half the measured shortening to the patient’s shoe. If there is considerable pronation to the same foot, he says one should use an inversion strapping with the heel lift.

   Furthermore, the limb length discrepancy should correlate with a clinical examination of the subject’s gait, according to Dr. Skliar. He notes that if the center of gravity shifts to the short side, the longer limb may be externally rotated or the corresponding foot may be pronated with or without genu valgum. The shoulder of the longer limb is usually lower, yielding what he notes would appear to be a longer arm length.

   Dr. D’Amico assesses limb length via computer assisted gait analysis two weeks after dispensing the orthotic. He says parameters that are particularly important to be symmetrical include: calcaneal stance duration, single limb support, stance, swing, midstance and propulsive phases of gait.

   In his biomechanical examination, Dr. D’Amico notes the position and symmetry of the limbs first while the patient is seated. Then with the patient standing, he places his hands on the superior brim of the pelvis and notes any asymmetry. In this manner, one can easily observe discrepancies of less than ½ inch, according to Dr. D’Amico.

   Dr. D’Amico and Dr. Skliar recall seeing Richard O. Schuster, DPM, place a large carpenter’s level across the patient’s knees while he or she was seated to assess below knee shortages and then recheck it with the patient in neutral subtalar position.

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